Biology Paper 3 Marking Scheme - CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018 PRE-MOCK WITH MARKING SCHEME

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BIOLOGY
PAPER 3
PRACTICAL
March 2018
MARKING SCHEME

CATHOLIC DIOCESE OF KERICHO (CDK) EXAMS – 2018
PRE-MOCK
BIOLOGY PAPER 3
MARKING SCHEME

INSTRUCTIONS TO CANDIDATES

1. Answer all the three questions in the spaces provided
2. You are required to spend the first 15 minutes of the 1 ¾ hours allowed for this paper reading the whole paper carefully before commencing your work.

1.  
   1. Study the diagrams T1 and S1 carefully and answer the following questions:

      

      1. Name the parts labeled S2, S3, S4, S5 and S6. (5mks)
         S₂ – Pericarp;
         S₃ – Mesocarp;
         S₄ – Seed;
         S₅ – Endocarp;
         S₆ – Fruit stalk;
         
         
      2. Name the parts labeled T2, T3, T4 and T5. (4mks)
         T₂ – Remains of calyx;
         T₃ – Placenta;
         T₄ – Seed/ovule;
         T₅ – Funicles;
         
         
      3. Complete the following table showing the type of fruit and reasons for each answer
         
         

         Specimen	Type of fruit	Reasons
         S1	Drupe;	- Once seed; Accept: hard or stony endocarp; Fleshy mesocarp; basal placentation
         T1	Legume pod	- Two sutures/two lines of weakness. Accept: marginal placentation.

         
         
         
      4. Complete the table below showing method of dispersal and reasons for each answer.
         
         

         Specimen	Method of dispersal	Reasons
         S1	Animal	- Bright colour; accept: fleshy mesocarp
         T1	Mechanical (self-explosive mechanism	- Two lines of weakness

         
         
         
   2. You are provided with a fruit labeled V.
      1. Cut a transverse section through specimen V. Draw and label of the cut surfaces. (4mks)
         
         
         
         
         
      2. State the type of placentation of specimen V. (1mk)
         Axile;
         
         
      3. Squeeze out the juice from one of the halves of specimen V. Using the reagents provided carry out tests to identify the type of food substances present in the juice (3mks)
         
         

         Food substance	Procedure	Observation	Conclusion
         Reducing sugar;	- Add equal amount of Benedict’s soln. heat	- Colour to orange/brown	- Reducing sugars present
         Ascorbic acid or vitamin C	- Add juice dropwise to DCPIP	DCPIP discolourises	Ascorbic acid or vit C. present

         
         
         
         
2. Study the diagrams Q and R carefully and answer the following questions.

   

   1.  
      1. Name the phylum to which specimens R and Q belong. (1mk)
         Arthropoda
         
         
      2. State two reasons for your answer in a (i) above. (2mks)
         
         • Presence of exoskeleton;
         • have segmented body
   2.  
      1. Name the class to which each of R and Q belong (2mks)
         R - Insecta
         Q - Arachnida
         
         
      2. State reasons for your answer in (b) (i) above (2mks)
         R – three body regions; – three pairs of legs; One pair of antennae; One pair of compound eyes; One pair of spiracles per segment
         Q – Body divided into two parts (Cephalothorax and abdomen); Accept four pairs of walking legs
         
         
3. Study the diagrams set A1, set E1, set M1 and set B carefully and answer the questions below

   

   1. State the conditions under which each set up was grown. (3mks)
      Set A₁ – normal conditions
      Set E₁ – in the dark
      Set B – unidirectional light
      
      
   2.  
      1. Name the phenomenon exhibited by seedlings in set E1 (1mk)
         Etiolation
      2. Give a reason why plants exhibit the phenomenon named in (b) (i) above (1mk)
         To reach light
   3.  
      1. Name the response exhibited by the seedlings in set B. (1mk)
         Positive phototropism
      2. Explain how the response named in (c) (i) above occurred (2mks)
         Auxins move to the darker side causing faster growth on this side; resulting in curvature of the shoot towards the source of light;
   4.  
      1. State the type of germination exhibited by seedlings in set A1 and set M1. (2mks)
         Set A₁ – Epigeal;  Set M₁ – hypogeal; 1mk
         
         
      2. Give a reason for your answer in (d) (i) above (2mks)
         Set A₁ – cotyledons brought above the ground; Set M₁ – cotyledons remain below the earth’s surface/underground;